Damper in a washing machine and fabricating method of the same

ABSTRACT

A damper for a washing machine includes: a cylinder; a piston body having one end inserted into the cylinder; a first friction member interposed in a contact surface between the piston body and the cylinder; an extension bar extended from an inserted portion of the piston body, the extension bar having a circumferential stopper at the extended portion; a friction ring formed between the circumferential stopper and the first friction member; and a second friction member formed on an outer circumferential surface of the friction ring to contact with an inner surface of the cylinder.

TECHNICAL FIELD

The present invention relates to a damper structure, and moreparticularly to a multi-step damper structure of a washing machine and amethod for forming the same, in which a damping force is applied withmulti-steps according to an amount of vibration occurring in the washingmachine, and a large or small amount of vibration is attenuatedappropriately to thereby operate the washing machine in a low noisestate.

BACKGROUND ART

Washing machines are classified into a drum type, an agitator type and apulsator type according to a washing method. Specifically, the drumwashing machine has a protrusion portion formed on an inner wall of thecylinder. A washing operation is performed by an impact force occurringwhen a laundry is lifted up and dropped down along an innercircumferential surface of the drum due to the protrusion portion duringa rotation of the drum.

Recently, the drum washing machine is widely used since a laundry isless damaged and a small amount of washing water is used.

FIG. 1 is a schematic view of a general drum washing machine.

Referring to FIG. 1, the drum washing machine includes a case 3 having ahollow cuboid shape, a tub 1 accommodated in the case 3 to containwater, a drum 2 formed inside the tub 1 to receive a laundry, and adriving motor 10 installed in a back of the tub 1 to rotate the drum 2.

Herein, an operation of the general drum washing machine will bedescribed below.

First, a torque of the driving motor 10 is transferred to the drum 2through a belt 11. If the drum 2 rotates, the laundry loaded into thedrum 2 rotates together. At this time, the drum 2 rotates at a lowspeed. Therefore, if the laundry is placed in an upper portion of thedrum during a rotation of the drum, the laundry is dropped down due tothe gravity, so that the laundry collides with the washing watercontained in the tub 1. The laundry stained with dirt can be washed dueto the impact force occurring between the laundry and the washing water.

Additionally, the washing machine includes a weight pendulum 4 formed onone side of an outer circumference of the tub 1 to correct the center ofgravity in back and forth/right and left directions of the tub 1, aspring 5 connected between the case 3 and the tub 1 to relieve an amountof vibration occurring in the tub 1 and the drum 2, and a damper 8connected between the case 3 and the tub 1 to attenuate an amount ofvibration occurring in the tub 1.

The weight pendulum 4 fundamentally eliminates the vibration due to aneccentric center of gravity of the tub 1 by matching the center ofgravity of the tub 1.

Further, an amount of vibration due to the operation of the tub 1 isrelieved by the spring 5 and attenuated by the damper, thereby rapidlyattenuating an amount of vibration occurring during the operation of thetub 1.

In more detail, the damper 8 includes a cylinder 6 having one endportion connected to the tub 1, and a piston load 7 having one endportion connected to the case 3 and inserted into the cylinder 6.

FIG. 2 is a sectional view of a general damper.

Referring to FIG. 2, the general damper 8 includes the cylinder 6 andthe piston load 7 having some portion inserted into the cylinder 6. Thegeneral damper 8 further includes a tub fixing opening 61 for allowingthe piston load 7 to be connected to the tub 1, a case fixing opening 71for allowing some portion of the piston load 7 to be connected to thecase 3, a friction member 9 formed on one end portion of the piston load7 to perform a friction action with an inner circumferential surface ofthe cylinder 6, and a vent 72 formed inside the piston load 7 to preventan internal air of the cylinder 6 from being compressed.

Herein, an operation of the damper 8 will be described with reference tothe structure of the damper 8.

When a predetermined amount of vibration occurs in the tub 1 and/or thedrum 2, a relatively different displacement occurs in an innercircumferential surface of the cylinder 6 and an outer circumferentialsurface of the piston load 7. The vibration is converted into africtional heat due to the friction member 9 formed between the cylinder6 and the piston load 7. As a result, a frictional force of the tub 1and/or the drum 2 is converted into a heat of the friction member 9 andthen attenuated.

Additionally, in order to prevent the damper 8 from being damaged whenthe tub 1 is shaken in back and front/right and left directions,predetermined hole (e.g., circular hole) is formed in the tub fixingopening 61 and the case fixing opening 71, so that the damper 8 is fixedto the tub 1 and the case 3 in a freely movable state. In order toprevent the damping force from being lowered due to a compression of aninternal air of the cylinder 6 when the piston load 7 moves in a leftdirection with reference to the drawing, the vent 72 forms a passagethrough which air is exhausted.

Meanwhile, the case of large amount of vibration and the case of smallamount of vibration may occur in the drum washing machine. For example,a large amount of vibration occurs since a change in a drum rotationspeed is great during an intermittent dewatering mode, and a smallamount of vibration occurs since a change in a drum rotation speed issmall during a continuous dewatering mode.

However, the same damping force is always generated in the generaldamper 8, as described above. Therefore, in case a small amount ofvibration occurs, the damper 8 acts as a rigid body, such that an amountof vibration cannot be rapidly attenuated due to a vibration exceeding adisplacement limit of the damper 8 and the damper 8 may be damaged.Considering this, it is usual to form the damper 8 to match the case alarge amount of vibration occurs.

Since such a conventional damper cannot properly cope with the change inan amount of vibration, noise and vibration occur seriously, therebycausing an inconvenience of use.

In other words, there is a demand for a damper which can apply a largedamping force when a large amount of vibration is generated and canapply a small damping force when a small amount of vibration isgenerated, thereby rapidly reducing the vibration and noise.

DISCLOSURE OF THE INVENTION

Accordingly, the present invention is directed to a damper for a washingmachine that substantially obviates the problems caused by limitationsand disadvantage of the conventional one.

One object of the present invention is to provide a damper for a washingmachine, in which an appropriate damping force is applied in case alarge or small amount of vibration is generated, thereby rapidlyreducing an amount of vibration.

Another object of the present invention is to provide a damper for awashing machine, in which an appropriate damping force is applied torapidly reduce an amount of vibration, and an amount of noise occurringdue to a collision of parts during a generation of vibration.

Further another object of the present invention is to provide a damperfor a washing machine, which is capable of preventing a damage of thedamper.

To achieve the above objects, the present invention provides a damperfor a washing machine, comprising: a cylinder; a piston body having oneend inserted into the cylinder; a first friction member interposed in acontact surface between the piston body and the cylinder; an extensionbar extended from an inserted portion of the piston body, the extensionbar having a circumferential stopper at the extended portion; a frictionring formed between the circumferential stopper and the first frictionmember; and a second friction member formed on an outer circumferentialsurface of the friction ring to contact with an inner surface of thecylinder.

In accordance with another aspect of the present invention, a damper fora washing machine comprises: a cylinder; a piston body having one endinserted into the cylinder; a first friction member interposed betweenthe piston body and the cylinder; an extension bar extended from aninserted portion of the piston body, the extension bar including acircumferential stopper expandedly formed at a predetermine position ofthe extended portion; a friction ring formed between the circumferentialstopper and the piston body and operated by the circumferential stopperand the piston body; and a second friction member interposed in acontact portion between the friction ring and the cylinder.

In accordance with another aspect of the present invention, a damper fora washing machine includes: a cylinder; a piston body having one endportion inserted into the cylinder and a hollow central portion; a firstfriction member interposed between the piston body and the cylinder; anextension bar having one end portion insertedly fixed to the centralportion of the piston body and the other end portion extended from thepiston body, the extension bar including a circumferential stopperexpandedly formed at the extended end portion; a friction ring formedbetween the circumferential stopper and the piston body and operated bythe circumferential stopper and the piston body; and a second frictionmember interposed in a contact portion between the friction ring and thecylinder.

In accordance with another aspect of the present invention, a method forforming a damper for a washing machine includes the steps of: connectingan elastic member to an end portion of a piston body, connecting anotherelastic member to an extension bar, and placing a friction ring in anouter circumference of the extension bar; inserting one end portion ofthe extension bar into the piston body to fix the extension bar and thepiston body by means of a stopper structure; and inserting a combinationof the extension bar and the piston body into the cylinder.

In accordance with another aspect of the present invention, a damper fora washing machine includes: a cylinder; a piston body having one endportion inserted into the cylinder; a first friction member disposed ina contact surface between the piston body and the cylinder; an extensionbar extended from an inserted portion of the piston body, the extensionbar including a circumferential stopper formed on the extended portion;a friction ring inserted into the cylinder, the friction ring includinga friction ring stopper some portion of which is contracted; and asecond friction member formed on an outer circumferential surface of thefriction ring to contact with an inner surface of the cylinder.

In accordance with another aspect of the present invention, a damper fora washing machine includes: a cylinder; a piston body having one endportion inserted into the cylinder; a first friction member interposedbetween the piston body and the cylinder; an extension bar extended froman inserted portion of the piston body; a friction ring formed on anouter side spaced apart from the extension bar; a friction ring rotationpreventing means for preventing a rotation of the friction ring; and asecond friction member formed on an outer circumferential surface of thefriction ring to contact with an inner surface of the cylinder.

In accordance with a another aspect of the present invention, a damperfor a washing machine includes: a cylinder; a piston body having one endportion inserted into the cylinder; a first friction member interposedin a contact surface between the piston body and the cylinder; anextension bar extended from an inserted portion of the piston body, theextension bar including a circumferential stopper formed on the extendedportion; a friction ring formed between the circumferential stopper andthe first friction member, the friction ring including a reinforcementrib protrudedly formed on an inner circumferential surface; and a secondfriction member formed on an outer circumferential surface of thefriction ring to contact with an inner surface of the cylinder.

In accordance with another aspect of the present invention, a damper fora washing machine includes: a cylinder; a piston body having one endportion inserted into the cylinder, and an extension bar extended fromthe piston body and having a diameter smaller than the piston body, thepiston body and the extension bar being formed as one body; a firstfriction member interposed in a contact surface between the piston bodyand the cylinder; a friction ring formed between the extension bar andthe first friction member; and a second friction member formed on anouter circumferential surface of the friction ring and contacting withan inner surface of the cylinder.

In accordance with another aspect of the present invention, a method forforming a damper for the washing machine includes the steps of:inserting a friction ring into an outer side spaced apart from anextension bar; arranging a circumferential stopper in one end of theextension bar to fix the circumferential stopper; and inserting theextension bar into a cylinder.

The damper for the washing machine and the method for forming the samecan rapidly reduce an amount of vibration occurring in the washingmachine.

Further, it is possible to prevent the damper from being damaged due toa large amount of vibration.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects, other features and advantages of the presentinvention will become more apparent by describing the preferredembodiments thereof with reference to the accompanying drawings, inwhich:

FIG. 1 is a schematic view of a conventional durum washing machine;

FIG. 2 is a sectional view of a conventional damper for a washingmachine;

FIG. 3 is a sectional view of a damper for a washing machine accordingto a first embodiment of the present invention;

FIG. 4 is a sectional view showing the case that a contractile force isapplied to a damper for a washing machine according to a firstembodiment of the present invention;

FIG. 5 is a sectional view showing the case that a tensile force isapplied to a damper for a washing machine according to a firstembodiment of the present invention;

FIG. 6 is a graph showing a relationship between a displacement of acylinder and a damping force in a damper for a washing machine accordingto a first embodiment of the present invention;

FIG. 7 is a sectional view of a damper for a washing machine accordingto a second embodiment of the present invention;

FIG. 8 is a sectional view of a damper for a washing machine accordingto a third embodiment of the present invention;

FIGS. 9 and 10 are sectional views showing an operation of the damperfor the washing machine according to the third embodiment of the presentinvention;

FIG. 11 is a sectional view of a damper for a washing machine accordingto a fourth embodiment of the present invention;

FIGS. 12 and 13 are sectional views showing an operation of the damperfor a washing machine according to the fourth embodiment of the presentinvention;

FIG. 14 is an exploded perspective view of the damper for the washingmachine according to the fourth embodiment of the present invention;

FIG. 15 is a flowchart showing a method for forming the damper for thewashing machine according to the fourth embodiment of the presentinvention;

FIG. 16 is a sectional view of a damper for a washing machine accordingto a fifth embodiment of the present invention;

FIG. 17 is a sectional view of a damper for a washing machine accordingto a sixth embodiment of the present invention;

FIGS. 18 and 19 are sectional views showing an operation of a damper fora washing machine according to a sixth embodiment of the presentinvention;

FIG. 20 is a sectional view of a damper for a washing machine accordingto a seventh embodiment of the present invention;

FIG. 21 is a sectional view of a damper for a washing machine accordingto an eighth embodiment of the present invention;

FIGS. 22 and 23 are sectional views showing an operation of a damper fora washing machine according to the eighth embodiment of the presentinvention;

FIG. 24 is a sectional view of a damper for a washing machine accordingto a ninth embodiment of the present invention;

FIG. 25 is a sectional view of a damper for a washing machine accordingto a tenth embodiment of the present invention;

FIG. 26 is a sectional view taken along the line A-A′ of FIG. 25;

FIG. 27 is a sectional view of a damper for a washing machine accordingto an eleventh embodiment of the present invention;

FIG. 28 is a sectional view taken along the line A-A′ of FIG. 25according to a twelfth embodiment of the present invention;

FIG. 29 is a sectional view taken along the line A-A′ of FIG. 25according to a thirteenth embodiment of the present invention;

FIG. 30 is a sectional view taken along the line A-A′ of FIG. 25according to a fourteenth embodiment of the present invention;

FIG. 31 is a sectional view of a damper for a washing machine accordingto a fifteenth embodiment of the present invention;

FIG. 32 is an enlarged view of the portion “A” of FIG. 31;

FIG. 33 is a sectional view of a damper for a washing machine accordingto a sixteenth embodiment of the present invention;

FIG. 34 is an enlarged view of the portion “A” of FIG. 33;

FIG. 35 is a sectional view of a damper for a washing machine accordingto a seventeenth embodiment of the present invention;

FIG. 36 is an enlarged view of the portion “A” of FIG. 35;

FIG. 37 is a sectional view of a damper for a washing machine accordingto an eighteenth embodiment of the present invention;

FIG. 38 is an enlarged view of the portion “A” of FIG. 37;

FIG. 39 is a sectional view of a damper for a washing machine accordingto a nineteenth embodiment of the present invention;

FIG. 40 is an exploded perspective view of a damper for a washingmachine according to a nineteenth embodiment of the present invention;

FIG. 41 is a flowchart showing a method for forming a damper for awashing machine according to the nineteenth embodiment of the presentinvention; and

FIG. 42 is a sectional view of a damper for a washing machine accordingto a twentieth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the attached drawings.

FIGS. 3 to 6 illustrate a first embodiment of the present invention.

FIG. 3 is a sectional view of a damper for a washing machine accordingto a first embodiment of the present invention.

Referring to FIG. 3, the damper for the washing machine includes ahollow cylinder 100, a piston body 200 inserted into the hollow portionof the cylinder 100, an extension bar 300 coupled to the piston body 200and extended therefrom, and a circular friction ring 400 thatsurficially contacts with an inner circumferential surface of thecylinder 100 in a state that a free movement is possible because apredetermined interval is maintained with an outer circumferentialsurface of the extension bar 300.

Additionally, the damper for the washing machine includes a tub fixingopening 110 formed at one end portion of the cylinder 100 and connectedto a tub of the washing machine, a case fixing opening 240 formed at oneend portion of the piston body 200 and connected to a case of thewashing machine, a first friction member 210 formed on an outercircumferential surface of the other end portion of the piston body 200to cause a frictional action, and a plurality of cooling fins 220elongatedly formed on an outer circumferential surface of the pistonbody 200 to emit a frictional heat out of the damper. Specifically, thefirst friction member 210 can be formed on a left end portion of thepiston body in order to lengthen a movement distant of the piston body200 to the maximum.

Further, the damper for the washing machine includes a second frictionmember 410 formed on an outer circumferential surface of the frictionalring 400 to cause a frictional action with the inner circumferentialsurface of the cylinder 100, and a fitting protrusion 401 for allowingthe second friction member 410 to be fitted into the friction ring 400.

Further, the first and second friction members 210 and 410 can beprovided with a porous plastic coated with a lubricant. Here, viscousfluids such as grease can be used as the lubricant.

Further, the damper for the washing machine includes an elasticallydeformable opening 320 formed on one end portion of the extension bar300, and a fixing groove 230 formed on a predetermined position of thepiston body 200 and to which the elastically deformable opening 320 isinsertedly fixed. A circumferential stopper 310 is formed on the otherend portion of the extension bar 300. When the piston body 200 moves ina right direction on the drawing, that is, when the cylinder 100 movesin a left direction, the friction ring 400 is caught by thecircumferential stopper 310.

Herein, an operation of the damper for the washing machine according tothe present invention will be described in brief.

In a state that the tub fixing opening 110 and the case fixing opening240 are respectively connected to the tub and the case of the washingmachine, an amount of vibration due to an operation of the washingmachine is transferred through the tub fixing opening 110 to the damper.Therefore, the amount of the vibration occurring in the washing machinecauses a displacement of the cylinder 100 and the cylinder 100 movesrelatively with respect to the piston body 200 fixed to the case andstopped therein.

If the cylinder 100 moves, the amount of the vibration is attenuated dueto a damping force, which is generated due to a frictional force betweenthe inner circumferential surface of the cylinder 100 and the outercircumferential surface of the first friction member 210. Meanwhile, ifthe displacement of the cylinder 100 is great due to a large amount ofthe vibration, the friction ring 400 contacts with the circumferentialstopper 310 and the left end portion of the piston body 200, so that africtional force is generated in the second friction member 410 with thesame electricity as the first friction member 210.

In more detail, if the displacement of the cylinder 100 is small due toa small amount of the vibration, a small damping force occurs because africtional force is generated only between the inner circumferentialsurface of the cylinder 100 and the first friction member 210. However,if the displacement of the cylinder 100 is great due to a large amountof the vibration, a frictional force is generated between the innercircumferential surface of the cylinder 100 and the second frictionmember 410, as well as between the inner circumferential surface of thecylinder 100 and the first friction member 210. As a result, a largerdamping force occurs.

As described above, in case that the amount of the vibration is small, asmall frictional force or damping force is applied, and in case that theamount of the vibration is great, a large frictional force or dampingforce is applied. Therefore, a large or small damping force is appliedaccording to the specific cases, that is, the amount of the vibration.For example, if a large amount of the vibration occurs like anintermittent dewatering mode, the frictional force is generated betweenthe first and second friction members 210 and 410 and the innercircumferential surface of the cylinder 100, thus causing a largedamping force. However, if a small amount of the vibration occurs like acontinuous dewatering mode, the frictional force is generated onlybetween the first friction member 210 and the inner circumferentialsurface of the cylinder 100, thus causing a small damping force.

Meanwhile, the elastically deformable opening 320 is provided for stablyassembling the extension bar 300 and the piston body 200 and makes itpossible to fix the extension bar 300 to the piston body 200 in wholeafter the friction ring 400 is inserted into the extension bar 300. Inother words, if one end portion of the extension bar 300 is fit into thepiston body 200 after the friction ring 400 is inserted into the outercircumferential surface of the extension bar 300, the opening 320 isdeformed elastically. Then, if the extension bar 300 is completelyinserted and thus reaches a position where the fixing groove 230 and theelastically deformable opening 320 are arranged, the elasticallydeformable opening 320 is recovered and inserted into the fixing groove230. Through the above assembly process, the extension bar 300 and thepiston body 200 can be completely and fixedly combined with each other.

FIG. 4 is a sectional view showing the case that a contractile force isapplied to the damper for the washing machine according to the presentinvention, and FIG. 5 is a sectional view showing the case that atensile force is applied to the damper for the washing machine accordingto the present invention. Herein, the operation of the damper accordingto the present invention will be described below in detail.

Referring to FIGS. 4 and 5, in case the contractile force is applied,the cylinder 100 moves in a right direction (an arrow direction of FIG.4). In more detail, when the cylinder 100 moves in the right direction,a frictional force is generated in a contact surface between the innercircumferential surface of the cylinder 100 and the first frictionmember 210 because the first friction member 210 is still. However, thesecond friction member 410 and the friction ring 400 move in the rightdirection together with the cylinder 100. Therefore, no frictional forceis generated in a contact surface between the friction ring 400 and thecylinder 100. In order to make the friction member 410 and the frictionring 400 move together with the cylinder 100, the inner circumferentialsurface of the friction member 410 and the outer circumferential surfaceof the extension bar 300 are not fixed and can be spaced apart from eachother by a predetermined interval.

Further, if the movement distance of the cylinder 100 exceeds “L1”, thefriction ring cannot move together with the cylinder 100 any morebecause the left portion of the piston body 200 contacts with the rightportion of the friction ring 400. Therefore, after that time, thefrictional force applied to the cylinder 100 is a sum of the frictionalforces of the first and second friction members 210 and 410.

Meanwhile, in case the tensile force is applied to the damper, thecylinder 100 moves in the left direction (an arrow direction of FIG. 5).When the cylinder 100 moves in the left direction, a frictional force isgenerated in a contact surface between the inner circumferential surfaceof the cylinder 100 and the first friction member 210 because the firstfriction member 210 is still with respect to the cylinder 100. However,the second friction member 410 and the friction ring 400 move in theleft direction together with the cylinder 100. In order to make thefriction member 410 and the friction ring 400 move together with thecylinder 100, the inner circumferential surface of the friction member410 and the outer circumferential surface of the extension bar 300 arenot fixed and can be spaced apart from each other by a predeterminedinterval.

If the cylinder 100 continues to move and the movement distance of thecylinder 100 exceeds “L2”, the friction ring cannot move together withthe cylinder 100 any more because the circumferential stopper 310contacts with the left portion of the friction ring 400. Therefore,after that time, the frictional force applied to the cylinder 100 is asum of the frictional forces of the first and second friction members210 and 410.

FIG. 6 is a graph showing a relationship between the displacement of thecylinder and the damping force in the damper for the washing machineaccording to the present invention.

In FIG. 6, a horizontal axis is the displacement (L) of the cylinder anda vertical axis is the damping force (F) generated by the damper.Herein, the operation of the damper will be described below in detailwith reference to FIG. 6.

When the cylinder 100 moves in the right direction (the arrow directionof FIG. 4) due to an external force, only a damping force (F1) derivedfrom a small frictional force caused by the first friction member 210 isapplied till before the displacement (L) reaches a predetermineddistance (L1). Then, if the cylinder 100 continues to move and exceedsthe predetermined distance (L1), a frictional force is generated due toboth the first and second friction members 210 and 410 at the same time.A damping force (F1+F2) derived from a large frictional force caused bythe first and second friction members 210 and 410 is applied. Therefore,the vibration can be attenuated rapidly in a noiseless state by applyinga small damping force with respect to a small vibration having a smalldisplacement. In addition, the vibration can be attenuated rapidlywithout noise and damage of the damper due to a large frictional forceand a large damping force by applying a large damping force with respectto a large vibration having a large displacement.

Further, when the cylinder 100 moves in the left direction (the arrowdirection of FIG. 5) due to an external force, only a damping force (F1)derived from a small frictional force caused by the first frictionmember 210 is applied till before the displacement (L) reaches apredetermined distance (L2). Then, if the cylinder 100 continues to moveand the displacement (L) exceeds the predetermined distance (L2), africtional force is generated due to both the first and second frictionmembers 210 and 410 at the same time. A damping force (F1+F2) derivedfrom a large frictional force caused by the first and second frictionmembers 210 and 410 is applied. Therefore, the vibration can beattenuated rapidly in a noiseless state by applying a small dampingforce with respect to a small vibration having a small displacement. Inaddition, the vibration can be attenuated rapidly without noise anddamage of the damper due to a large frictional force and a large dampingforce by applying the large damping force (F1+F2) with respect to alarge vibration having a large displacement.

In other words, the vibration can be attenuated rapidly in a noiselessstate with respect to any amount of the vibration by applying differentdamping forces to the damper according to the amount of the vibrationand the magnitude of the displacement.

Further, in this embodiment, the positions of the cylinder 100 and thepiston body 200 can be changed. In other words, the cylinder 100 and thepiston body 200 can be connected to the case side and the tub side,respectively.

Further, the cylinder 100 and the piston body 200 are connected to thetub and the case of the washing machine in a direction that the firstand second fixing openings 110 and 240 are crossed with each other. Inother words, if a hole of the first fixing opening 110 is positioned ina vertical direction, a hole of the second fixing opening 240 ispositioned in a horizontal direction, and vice versa. In this manner, inaddition to a length direction of the damper, the vibration can beattenuated somewhat with respect to a width direction of the damperaccording to the fundamental function of the damper. Furthermore, it ispossible to prevent the damper from being damaged due to the vibration.

FIG. 7 is a sectional view of a damper for a washing machine accordingto a second embodiment of the present invention

Referring to FIG. 7, a structure of the damper for the washing machineaccording to the second embodiment of the present invention is mostlysimilar to that of the damper according to the first embodiment of thepresent invention. A difference is that a third friction member 420except for the second friction member 410 is additionally formed on theouter circumferential surface of the friction ring 410. By doing so, thedamping force applied to the damper is generally increased much more.

In other words, the damping force (F1) is identical to the firstembodiment till before the displacement of the cylinder 100 reaches apredetermined distance. On the other hand, if the displacement of thecylinder 100 exceeds the predetermined distance, a damping force islarger than the damping force (F1+F2) of the first embodiment. As aresult, the vibration can be attenuated more rapidly by applying thefrictional force caused by the first to third friction members 210, 410and 420.

Further, due to a condition that widths of the friction members 410 and420 are limited to a predetermined length, this embodiment can beapplied conveniently to the case that the respective friction membersmust be used separately.

FIGS. 8 to 10 illustrate a third embodiment of the present invention.

Referring to FIG. 8, a structure of the damper for the washing machineaccording to the third embodiment of the present invention is mostlysimilar to that of the damper according to the first embodiment of thepresent invention. A difference is that the damper according to thethird embodiment of the present invention further includes a firstelastic member 320 formed on an end portion of the piston body 200, anda second elastic member 340 formed on an inner surface of thecircumferential stopper 310.

In more detail, the second elastic member 340 of a soft elasticmaterial, such as a rubber, is inserted into the inner surface of thecircumferential stopper 310 in order to allow the circumferentialstopper 310 and the friction ring 400 to softly contact with each otherwithout any impact. Herein, an effect of the second elastic member 340will be described below. Since a large vibration occurs with a shortfrequency at a high speed operation of the washing machine, thecircumferential stopper 310 and the friction ring 400 contact with eachother at a fast speed. The strong impact due to the contact acts as anoise. Therefore, the inserted second elastic member 340 of a softmaterial can relieve the impact occurring at the contact surface.

FIGS. 9 and 10 are sectional views illustrating an operation of thedamper for the washing machine according to the third embodiment of thepresent invention. In more detail, FIGS. 9 and 10 are sectional viewsshowing the cases that a contractile force and a tensile force areapplied to the damper for the washing machine according to the thirdembodiment of the present invention, respectively. In the drawings, anoperational mechanism of reducing the vibration and noise is identicalto the first embodiment of the present invention. However, in case themovement distance of the cylinder 100 exceeds “L1” and “L2” and thefriction ring 400 contacts with and collides the end portion of thecircumferential stopper 310 and/or the end portion of the piston body200, the impact force can be relieved sufficiently due to the firstelastic member 330 and/or the second elastic member 340.

Since the impact forces occurring at the respective contact surfaces canbe relieved due to the first and second elastic members 330 and 340, itis possible to prevent the degradation of the respective parts and theoccurrence of noise and vibration.

FIGS. 11 to 15 illustrate a fourth embodiment of the present invention.A structure of the damper for the washing machine according to thefourth embodiment of the present invention is mostly similar to that ofthe damper according to the third embodiment of the present invention. Adifference is a forming process and structure of the elastic member forrelieving the impact.

Herein, the structure of the damper according to the fourth embodimentof the present invention will be describe below with reference to FIG.11. Referring to FIG. 11, the damper for the washing machine accordingto the fourth embodiment of the present invention includes a cylinder100, a piston body 200, an extension bar 300, a circular friction ring400, a tub fixing opening 110, a case fixing opening 240, a firstfriction member 210, a second friction member 410, a cooling fin 220, anelastically deformable opening 320, an elastically deformable openingstopper 321 formed on an end portion of the elastically deformableopening 320 to fix the extension bar 300 to the piston body 200, afixing groove 230, a circumferential stopper 310, a first elastic member330, and a second elastic member 340, which are similar to the thirdembodiment of the present invention.

In this embodiment, the damper according to the fourth embodiment of thepresent invention further includes an insertion protrusion 341 and asecond elastic member insertion hole 311 in order to allow the secondelastic member 340 to be fitted. The insertion protrusion 341 isprotrudedly formed on one surface of the second elastic member 340, andthe second elastic member insertion hole 311 is formed by opening thecircumferential stopper 310 in order to allow the insertion protrusion341 to be arranged and fitted.

Specifically, a predetermined protrusion can be further formed on a bodyof the insertion protrusion 341 in order to allow the insertionprotrusion 341 not to be released after the insertion protrusion 341 isfitted into the second elastic member insertion hole 311.

Further, the first elastic member 330 is formed in a circular shape sothat it can be fitted into the piston body 200. The damper according tothe fourth embodiment of the present invention further includes at leastone first elastic member hook protrusion 331 formed on one surface ofthe circular first elastic member 330, a first elastic member insertiongroove 250 formed on one end portion of the piston body 200 in order toallow a cylinder of the first elastic member 330 to be fitted into aninside of the piston body 200, and a first elastic member hook groove260 formed on a position in which the first elastic member hookprotrusion 331 is arranged in the first elastic member insertion groove250.

Herein, an installation operation of the first elastic member 330 willbe described below. First, the first elastic member insertion groove 250is formed in a length direction of the piston body 200 and the firstelastic member hook protrusion 331 is then inserted into the firstelastic member insertion groove 250. At this time, the first elasticmember 330 can be inserted in a predetermined arrangement direction sothat the first elastic member hook protrusion 331 and the first elasticmember hook groove 260 can be arranged. The first elastic member 330 canbe stably fixed at a position in which the first elastic member hookprotrusion 331 and the first elastic member hook groove 260 are arrangedand caught.

Further, a plurality of cooling holes 241 are formed on the piston body200 in order to emit an internal heat out of the damper. The coolingholes 241 rapidly disperse a frictional heat, which is generated duringan operation of the damper, out of the damper together with the coolingfin 220.

Herein, an installation operation of the extension bar 300 will bedescribed below. After the friction ring 400 is inserted into theextension bar 300, the extension bar 300 is made to be fixable to thepiston body 200 in whole. Specifically, if the friction ring 400 isinserted into the outer circumference of the extension bar 300 and oneend portion of the extension bar 300 is then inserted into the pistonbody 200, the elastically deformable opening 320 is deformed due to theelasticity. The extension bar 300 is completely inserted and thusreaches a position where the fixing groove 230 and the elasticallydeformable opening 320 are arranged and the elastically deformableopening stopper 321 is recovered and inserted into the fixing groove230. Through the above assembly process, the extension bar 300 and thepiston body 200 can be completely and fixedly combined with each other.

An operation of the damper for the washing machine according to thefourth embodiment of the present invention is identical to thataccording to the third embodiment of the present invention and will beeasily understood with reference to FIGS. 12 and 13.

FIG. 14 is an exploded perspective view of the damper for the washingmachine according to the fourth embodiment of the present invention.

As described above, it can be seen from FIG. 14 that the damper for thewashing machine includes the cylinder 100, the piston body 200, theextension bar 300, the friction ring 400, the first elastic member 330,the second elastic member 340, the first friction member 210, and thesecond friction member 410.

The plurality of cooling fins 220 are elongatedly formed on the outercircumferential surface of the piston body 200 in right/left direction.The fixing groove 230 is formed by depressing or opening the outercircumferential surface of the piston body 200 so that the elasticallydeformable opening stopper 321 can be deformed elastically and insertedthereinto. The cooling hole 241 rapidly emits the internal heat out ofthe piston body 200. The first elastic member hook groove 260 is caughtby the first elastic member hook protrusion 331 to fix the position ofthe first elastic member 330 as a whole.

The right end portion of the extension bar 300 is divided up and down toform the elastically deformable opening 320, which is elasticallydeformed due to an external force. The elastically deformable openingstopper 321 is protrudedly formed on the end portion of the elasticallydeformable opening 320. The circumferential stopper 310 is expandedlyformed on the left end portion of the extension bar 300. The secondelastic member insertion hole 311 is formed on predetermined positionsof the circumferential stopper 310. At least one insertion protrusion341 is protrudedly formed on one side surface of the second frictionmember 340.

Herein, an assembly operation of the damper for the washing machine willbe described below.

FIG. 15 is a flowchart showing an assembly order of the damper for thewashing machine according to the fourth embodiment of the presentinvention.

Referring to FIG. 15, first, in order to form the damper for the washingmachine, the second elastic member 340 and the friction ring 400 areinserted into the extension bar 300 (ST11). At this time, the secondelastic member 340 is completely cohered to the circumferential stopper310 due to a predetermined stopper structure, so that the process offixing the extension bar 300 is easily performed.

The first friction member 330 is inserted into the piston body 200independently of the formation of the extension bar 300 (ST12).

After the extension bar 300 and the piston body 200 are assembled, theextension bar 300 is inserted into the piston body 200 so that theelastically deformable opening stopper 321 formed on the extension bar300 as one body can be fitted into the fixing groove 230 (ST13).

Finally, the combined object of the piston body 200 and the extensionbar 300 is inserted into the inside of the cylinder 100, thus completingthe damper for the washing machine (ST14).

Meanwhile, in the above assembly process, the connection of the firstfriction member 210 and the second friction member 410 can be performedin any steps till before the combined object of the piston body 200 andthe extension bar 300 is inserted into the inside of the cylinder 100.However, since the friction members 210 and 410 may be formed by rollingrectangular resin around a predetermined portion of the combined object,it is preferable to form the friction members 210 and 410 just beforethe combined object is inserted into the inside of the cylinder 100.

FIG. 16 illustrates a damper for a washing machine according to a fifthembodiment of the present invention.

Referring to FIG. 16, a structure of the damper for the washing machineaccording to the fifth embodiment of the present invention is mostlysimilar to that of the damper according to the third embodiment of thepresent invention. A difference is that first and second springs 360 and370 are formed instead of the first and second elastic members 330 and340.

In this embodiment, instead of the elastic member of the rubbermaterial, springs are disposed on the contact surface. Therefore, anappropriate position in which the friction ring 400 begins to operatecan be determined by adjusting a coefficient of elasticity.Additionally, since it is possible to prevent the contact between thefriction ring 400 and the circumferential stopper 310 and/or the contactbetween the friction ring 400 and the end portion of the piston body200, an amount of noise can be reduced much more. Specifically, theincrease or decrease of the damping force can be achieved more slowlydue to the friction ring 400 by slowly increasing the damping force,thereby improving a reduction effect of noise and vibration.

FIGS. 17 to 19 illustrate a sixth embodiment of the present invention.

FIG. 17 is a sectional view of the damper for the washing machineaccording to the sixth embodiment of the present invention. A structureof the damper for the washing machine according to the sixth embodimentof the present invention is mostly similar to that of the damperaccording to the first embodiment of the present invention. A differenceis a structure of a friction ring, a piston body and/or an extensionbar, which contact/contacts with the friction ring.

Like the conventional damper, the damper according to the presentinvention includes a cylinder 100, a piston body 200, an extension bar300, a friction ring 400, a tub fixing opening 110, a case fixingopening 240, a first friction member 210, a cooling fin 220, a secondfriction member 410, and a third friction member 420.

However, a left end portion of the friction ring 400 can maintain adiameter of the friction ring body without contraction in order to allowthe circumferential stopper 310 to pass smoothly. In order for thecircumferential stopper 310 to be caught, a right end portion of thefriction ring 400 includes a friction ring driving terminal 402 formedby reducing the diameter of the friction ring 400.

Additionally, a grease 390 is adhered to the respective contact surfaceof the friction ring 400, the extension bar 300 and the piston body 200.The detailed positions are represented by a reference numeral “390”. Thegrease 390 can relieve the frictional force among the respective membersand can also function to relieve a strong impact force among therespective members when the members are collided with each other.

Further, the damper according to the present invention includes anelastically deformable opening 320 formed on one end portion of theextension bar 300, and a fixing groove 230 into which the elasticallydeformable opening 320 is inserted. Further, the damper includes acircumferential stopper 310 formed on the other end portion of theextension bar 300. The circumferential stopper 310 functions to catchthe friction ring 400 when the piston body 200 moves in a rightdirection with reference to the drawing, that is, when the cylinder 100moves in a left direction with reference to the drawing. Specifically,since the circumferential stopper 310 is caught by the friction ringdriving terminal 402, an operation of the friction ring 400 is inducedwhen the extension bar 300 operates excessively, for example, when thecylinder 100 moves in the left direction with reference to the drawing.Of course, the friction ring 400 is caught by the left end portion ofthe piston body 200 and the operation of the friction ring 400 can beinduced.

Meanwhile, a margin that allows the extension bar 300 to move the rightand left directions is lengthened by forming the friction ring drivingterminal 402 on the right end portion of the friction ring 400, that is,the end portion of the piston body side. Specifically, if the frictionring driving terminal 402 is formed on the left end portion of thefriction ring 400, that is, not the piston body 200 but the oppositeside, the margin is shortened as much. Further, if the margin becomesnarrow, the damper may be damaged due to the strong impact force whenthe strong vibration of the tub causes the cylinder 100 to moveexcessively. Since the cylinder 100 must be long in order to form thefriction ring driving terminal 402 on the left end portion of thefriction ring 400 and to prevent the damage of the damper, it isundesired in view of a space utilization of the washing machine, adifficulty in the installation, and the like.

An operation of the damper for the washing machine according to thesixth embodiment of the present invention is identical to that describedin the first embodiment of the present invention. Therefore, itsdetailed description will be omitted. However, this embodiment ischaracterized in that the operation of the friction ring 400 can bestarted by the friction ring driving terminal 402 formed on the rightend portion of the friction ring 400. In other words, at a point of timewhen the circumferential stopper 310 contacts with the friction ringdriving terminal 402, the friction ring 400 may move in the rightdirection to increase the damping force. Or, at a point of time when theright end portion of the piston body 200 contacts with the friction ringdriving terminal 402, the friction ring 400 may move in the leftdirection to increase the damping force.

Further, the grease 390 is adhered to the main surface of the frictionring driving terminal 402 in order to relieve the impact force when thepiston body 200 and the circumferential stopper 310 contact with eachother centering on the friction ring driving terminal 402. The impact inthe collision can be buffered due to the grease 390. The presentinvention is not limited to the grease. In other words, any impactrelief material of a fluid form can be used as the grease 390.

Although the drawing shows that the end portion of the circumferentialstopper 310 is curved, the present invention is not limited to it. Evenwhen the end portion of the circumferential stopper 310 is formed in anon-curved shape, it does not influence an effect of the presentinvention.

FIG. 20 illustrates a seventh embodiment of the present invention. Astructure of the damper for the washing machine according to the seventhembodiment of the present invention is mostly similar to that of thedamper according to the sixth embodiment of the present invention. Adifference is that an elastic member instead of the grease (390, in FIG.7) is formed as a member for relieving the impact force during theoperation of the damper.

Specifically, first and second elastic members 330 and 340 are formed ata portion to which the grease 390 is adhered. Due to the elastic members330 and 340, an impact force is relieved at a portion with which thefriction ring contacts. The elastic members 330 and 340 can be adheredto or fitted into the piston body 200 and the circumferential stopper310, respectively. As a fitting method, the method described in thefourth embodiment of the present invention can be applied. Further, as amethod for relieving the impact force, the method described in the thirdembodiment of the present invention can be applied.

FIG. 21 is a sectional view of a damper for a washing machine accordingto an eighth embodiment of the present invention.

A structure of the damper for the washing machine according to theeighth embodiment of the present invention is mostly similar to that ofthe damper according to the sixth embodiment of the present invention.In this embodiment, a damping force can be increased by forming anotherfriction member at a portion extended from the circumferential stopper310 as one body. According to the structure according to the eightembodiment of the present invention, the damper for the washing machineincludes the circumferential stopper 310 and a fourth friction member350 formed at a portion extended from the circumferential stopper 310 toone side.

Specifically, the fourth friction member 350 is fixed to a body of theextension bar 300 and forms a contact surface with the innercircumferential surface of the friction ring 400. Therefore, when arelative displacement occurs between the extension bar 300 and thefriction ring 400, a damping force due to a friction of the contactsurface is generated.

As a result, when the cylinder 100 moves initially, the damping forcedue to the first friction member 210 and the damping force due to thefourth friction member 350 are generated at the same time. Here, thefirst friction member 210 is formed at the contact surface between theouter circumferential surface of the piston body 200 and the innercircumferential surface of the cylinder 100, and the fourth frictionmember 350 is formed at the contact surface between the outercircumferential surface of the extension bar 300 and the innercircumferential surface of the friction ring 400. In this manner, thedamping force can be increased much more due to the generation of theadditional damping force.

At this time, although only one of the first and fourth friction members210 and 350 is formed, it does not influence the e present invention. Inthis case, however, a frictional coefficient of the friction member usedin the first and fourth friction members 210 and 350 must be large inorder to generate the same damping force by using one damper.

Meanwhile, the fourth friction member 350 must have a frictionalcoefficient smaller than a sum of the frictional coefficients of thesecond and third friction members 410 and 420. If the frictionalcoefficient of the fourth friction member 350 is larger than the sum ofthe frictional coefficients of the second and third friction members 410and 420, the friction ring 400 moves at the same time when the extensionbar 300 moves. As a result, the friction ring 400 cannot move in amulti-stage.

An operation of the damper for the washing machine according to theeighth embodiment of the present invention will be described withreference to FIGS. 22 and 23.

First, if the contractile force is applied, the cylinder 100 moves in aright direction (an arrow direction of FIG. 22). When the cylinder 100moves in the right direction, a frictional force is generated in acontact surface between the inner circumferential surface of thecylinder 100 and the first friction member 210 and between the innercircumferential surface of the friction ring 400 and the fourth frictionmember 350, because the first and fourth friction members 210 and 350are still. However, the second and third friction members 410 and 420and the friction ring 400 move in the right direction together with thecylinder 100. In order to operate the friction ring 400, the frictionalcoefficient of the fourth friction member 350 may be smaller than thoseof the second and third friction members 410 and 420.

Further, if the movement distance of the cylinder 100 exceeds “L1”, thefriction ring 400 cannot move together with the cylinder 100 any morebecause the left portion of the piston body 200 contacts with thefriction ring stopper 402. Therefore, after that time, the frictionalforce applied to the cylinder 100 is a sum of the frictional forces ofthe second and third friction members 410 and 420.

Further, in case the tensile force is applied to the damper, thecylinder 100 moves in the left direction (an arrow direction of FIG.23). When the cylinder 100 moves in the left direction, a frictionalforce is generated in the contact surface between the innercircumferential surface of the cylinder 100 and the first frictionmember 210 and the contact surface between the inner circumferentialsurface of the friction ring 400 and the fourth friction member 350,because the first friction member 210 is still with respect to thecylinder 100 and the fourth friction member 350 is still with respect tothe friction ring 400. However, the second and third friction members410 and 420 and the friction ring 400 move in the left directiontogether with the cylinder 100.

If the cylinder 100 continues to move and the movement distance of thecylinder 100 exceeds “L2”, the friction ring cannot move together withthe cylinder 100 any more because the circumferential stopper 310contacts with the friction ring driving terminal 402. Therefore, afterthat time, the frictional force applied to the cylinder 100 is a sum ofthe frictional forces of the second and third friction members 410 and420.

This embodiment of the present invention has an effect that the dampingforce in the initial operation of the cylinder 100 can be increased muchmore.

Meanwhile, in this embodiment, the damping force according to theoperation of the cylinder 100 can be controlled more variously byadjusting the frictional coefficients of the first to fourth frictionmembers 210, 410, 420 and 350.

FIG. 24 illustrates a ninth embodiment of the present invention.

Referring to FIG. 24, a difference between the ninth embodiment and theeighth embodiment is that elastic members 330 and 340 are formed insteadof the grease 390. Specifically, a second elastic member 340 is formedof an elastic material on the inner surface of the circumferentialstopper 310, and a first elastic member 330 is formed of an elasticmaterial on the left end portion of the piston body 200. The first andsecond elastic members 330 and 340 can be formed of a rubber material.In this manner, when the circumferential stopper 310 and the right endportion of the piston body 200 contact with the friction ring drivingterminal 402, the impact force can be relieved by additionally formingthe elastic members 330 and 340. Particularly, in case a bufferingeffect cannot be obtained through the grease 390 alone when aconsiderable amount of the impact force is applied to the contactsurface of the friction ring driving terminal 402 due to a high speedrotation of the washing machine, the installation of the elastic members330 and 340 is required especially.

FIGS. 25 and 26 illustrate a tenth embodiment of the present invention.

A structure of the damper for the washing machine according to the tenthembodiment of the present invention is mostly similar to that of thedamper for the washing machine according to the first embodiment of thepresent invention. A difference is that a friction ring rotationpreventing means is formed in order to prevent the rotation of thesecond friction member 410. If the friction ring 400 rotates, the secondfriction member 410 also rotates. At this time, the second frictionmember 410 provided with a porous plastic coated with a lubricant may befolded or protruded externally. If an original shape of the secondfriction member 410 is changed, an appropriate frictional coefficient isnot reached on the contact surface between the second friction member410 and the cylinder 100. Therefore, the function of the damper cannotbe performed.

Accordingly, the friction ring rotation preventing means is formed inorder to prevent the rotation of the friction ring 400, as shown in FIG.26. FIG. 26 is a sectional view taken along the line A-A′ of FIG. 25.Referring to FIG. 26, the damper according to the present inventionincludes a cylinder 100, a second friction member 410, a friction ring400 and an extension bar 300. Specifically, the outer circumference ofthe friction ring 400 and the inner circumference of the cylinder 100are formed in a non-circular shape, for example, in an elliptical shapeas shown in FIG. 26. The second friction member 410 surrounding theouter circumference of the friction ring 400 is also formed in theelliptical shape. The second friction member 410 can be formed byinserting a rectangular porous plastic of elastic material, as describedabove. Therefore, without considering the shape at the formation of thesecond friction member 410, the second friction member 410 can be formedspontaneously in the elliptical shape while it is inserted into theouter circumference of the friction ring 400.

Since the outer circumference of the friction ring 400 and the innercircumference of the cylinder 100 are inserted in the elliptical shapein the above manner, an installation direction of the friction ring 400can be placed at an original position as it is without any movementduring the operation of the damper.

Since the installation direction of the friction ring 400 is fixed, itis possible to prevent in advance the second friction member 410 frombeing folded, which may be caused by the position movement of thefriction ring 400 during the operation of the damper. Additionally,since the second friction member 410 is not folded, the frictional forceoccurring in the friction ring 400 can maintain the value given when thefriction ring 400 is installed. As a result, the reliability can bemaintained in the operation of the damper.

This embodiment can obtain a great effect in case the position of thesecond friction member 410 is greatly changed in a state of high speedrotation, in which an amount of vibration reaches 2000 Hz.

FIG. 27 is a sectional view taken along the line A-A′ of FIG. 25,showing a damper for a washing machine according to an eleventhembodiment of the present invention. A structure of the damper for thewashing machine according to the eleventh embodiment of the presentinvention is mostly similar to that of the damper according to the tenthembodiment of the present invention. A difference is a structure of thefriction ring rotation preventing means.

In the friction ring rotation preventing structure of the damper for thewashing machine according to the eleventh embodiment of the presentinvention, the outer circumference of the extension bar 300 and theinner circumference of the friction ring 400 are formed in anon-circular shape, for example, in an elliptical shape as shown in FIG.27, in order to prevent the rotation of the friction ring 400.

In this manner, the friction ring 400 is fixed only in an installationdirection guided by the shape of the extension bar 300 and the frictionring 400 does not move the other directions. In other words, since therotation of the friction ring 400 is prevented, the friction ring 400 isstopped at a position set in the installation and does not rotate.

Since an effect obtained by preventing the rotation of the friction ring400 is identical to that of the tenth embodiment, its detaileddescription will be omitted.

FIG. 28 is a sectional view taken along the line A-A′ of FIG. 25,showing a damper for a washing machine according to a twelfth embodimentof the present invention. A structure of the damper for the washingmachine according to the twelfth embodiment of the present invention ismostly similar to that of the damper according to the tenth embodimentof the present invention. A difference is a structure of the frictionring rotation preventing means.

Referring to FIG. 28, the friction ring rotation preventing structure ofthe damper for the washing machine according to the twelfth embodimentof the present invention includes a spline 301 formed between the innercircumferential surface of the friction ring 400 and the outercircumferential surface of the extension bar 300.

The spline 301 is characterized in that the rotation of the frictionring 400 can be prevented by forming a discontinuous portion at one sidebetween the friction ring 400 and the extension bar 300.

Since an effect obtained by forming the spline 301 is identical to thatof the tenth embodiment, its detailed description will be omitted.

Meanwhile, the spline 301 can be formed between the outercircumferential surface of the friction ring 400 and the innercircumferential surface of the cylinder 100. In other words, apart fromthe interposition of the second friction member 410 between the frictionring 400 and the cylinder 100, in case the spline 301 is formed at apredetermined position of the contact surface between the friction ring400 and the cylinder 100, the rotation direction of the friction ring400 can be fixed without movement, as described above.

Meanwhile, the spline 301 must be formed in a state that a predeterminedinterval between the extension bar 300 and the friction ring 400 isinterposed. By doing so, the rotation direction of the friction ring 400is not twisted. Further, due to the frictional force of the secondfriction member 410, the friction ring 400 can move back and forthtogether with the cylinder 100 without regard to the extension bar 300.

FIG. 29 is a sectional view taken along the line A-A′ of FIG. 25,showing a damper for a washing machine according to a thirteenthembodiment of the present invention. A structure of the damper for thewashing machine according to the thirteenth embodiment of the presentinvention is mostly similar to that of the damper according to thetwelfth embodiment of the present invention. A difference is a structureof the friction ring rotation preventing means.

Referring to FIG. 29, a fixing key 302 is formed between the innercircumferential surface of the friction ring 400 and the outercircumferential surface of the extension bar 300.

Since the fixing key 302 prevents the friction ring 400 from beingrotated, a deformation of the second friction member 410 can beprevented. However, an interval between the extension bar 300 and thefriction ring 400 must be formed so that the friction ring 400 cannotrotate in the rotation direction and can freely rotate the up and downdirection (that is, the up and down direction of paper with respect tothe drawing). Therefore, the fixing key 302 is not forceably inserted.Preferably, the fixing key 302 is formed on one side of the frictionring 400 and the extension bar 300 as one body, and a groove into whichthe fixing key 302 is inserted is formed on the other side.

FIG. 30 is a sectional view taken along the line A-A′ of FIG. 25,showing a damper for a washing machine according to a fourteenthembodiment of the present invention. A structure of the damper for thewashing machine according to the fourteenth embodiment of the presentinvention is mostly similar to that of the damper according to thethirteenth embodiment of the present invention. A difference is astructure of the friction ring rotation preventing means.

Referring to FIG. 30, a serration 303 is formed between the frictionring 400 and the extension bar 300. The serration 303 prevents thefriction ring 400 from rotating freely, and the friction ring 400 can befixed in the original installation direction.

FIGS. 31 and 32 illustrate a fifteenth embodiment of the presentinvention.

FIG. 31 is a sectional view of the damper for the washing machineaccording to the fifteenth embodiment of the present invention. Astructure of the damper for the washing machine according to thefifteenth embodiment of the present invention is mostly similar to thatof the damper according to the first embodiment of the presentinvention. A difference is a structure of the friction ring 400 and theelastic member.

A third elastic member 332 is formed to surround at least the innercircumferential surface of the friction ring 400. It can be seen fromthe drawing that the third elastic member 332 surrounds the innercircumferential surface and both sides of the friction ring 400. Inother words, the third elastic member 332 surrounding the innercircumferential surface and both sides of the friction ring 400 isformed as one body. This structure can eliminate an inconvenience ofseparately inserting two elastic members 330 and 340 like the firstembodiment.

FIG. 32 is an enlarged view of the portion “A” of FIG. 31. As shown, thefriction ring 400 can move regardless of the extension bar 300 when thethird elastic member 332 and the outer circumferential surface of theextension 300 do not contact with each other. Therefore, a constantinterval must be maintained between the third elastic member 350 and theextension bar 300.

The elastic member can be installed in simpler manufacturing process byforming the third elastic member 332 as one body to surround the innercircumferential surface and both sides of the friction ring 400, asshown in the drawing.

FIGS. 33 and 34 illustrate a sixteenth embodiment of the presentinvention.

FIG. 33 is a sectional view of the damper for the washing machineaccording to the sixteenth embodiment of the present invention. Astructure of the damper for the washing machine according to thesixteenth embodiment of the present invention is mostly similar to thatof the damper according to the fifteenth embodiment of the presentinvention. A difference is a structure of the friction ring 400 and theelastic member.

A reinforcement rib 403 is further formed on the inner circumferentialsurface of the friction ring 400 to reinforce the strength of thefriction ring 400. The first and second elastic members 330 and 340 areformed in the same manner as the first embodiment. The impact forceoccurring during the operation of the damper can be buffered by makingthe elastic members contact with both sides of the friction ring 400.

Although this embodiment provides one reinforcement rib 403 formed onthe inner circumferential surface of the friction ring 400, the strengthof the friction ring 400 can also be increased in case two reinforcementribs are formed on both sides of the friction ring 400 or in case two ormore reinforcement ribs are formed on the entire inner circumferentialsurface of the friction ring 400.

FIG. 34 is an enlarged view of the portion “A” of FIG. 33. The principleoperation of the friction ring 400 can be performed by spacing apart thereinforcement rib 403 and the extension bar 300 from each other by apredetermined distance.

FIGS. 35 and 36 illustrate a seventeenth embodiment of the presentinvention.

FIG. 35 is a sectional view of the damper for the washing machineaccording to the seventeenth embodiment of the present invention. Astructure of the damper for the washing machine according to theseventeenth embodiment of the present invention is mostly similar tothat of the damper according to the sixteenth embodiment of the presentinvention. A difference is a structure of the friction ring 400 and theelastic member.

Unlike the sixteenth embodiment, diameters of the circumferentialstopper 310 and the end portion of the piston body 200 are reduced. Thefirst elastic member 330 is formed on the outer surface of the pistonbody 200 and the second elastic member 340 is formed on the innersurface of the circumferential stopper 310. Each diameter of thecircumferential stopper 310 and the piston body 200 are smaller thanthat of the end portion of the friction ring 400. Therefore, thecircumferential stopper 310 and the piston body 200 can pass the bothsides of the friction ring 400 and move inwardly much more. An imaginaryline represents such a height difference.

The circumferential stopper 310 and the piston body 200 entered inwardlythrough the end portion of the friction ring 400 contact with both sidesof the reinforcement rib 403, thus allowing the friction ring 400 to bemoved.

Therefore, a period during which a small damping force can be applied islengthened by a length between the end portion of the friction ring 400and the end portion of the reinforcement rib 403. Further, since thecontact portion of the friction ring 400 becomes the reinforcement rib402, the friction ring 400 can move in more stable state.

FIG. 36 is an enlarged view of the portion “A” of FIG. 35. The principleoperation of the friction ring 400 can be performed by spacing apart thereinforcement rib 403 and the extension bar 300 from each other by apredetermined distance.

FIGS. 37 and 38 illustrate an eighteenth embodiment of the presentinvention.

FIG. 37 is a sectional view of the damper for the washing machineaccording to the eighteenth embodiment of the present invention. Astructure of the damper for the washing machine according to theeighteenth embodiment of the present invention is mostly similar to thatof the damper according to the seventeenth embodiment of the presentinvention. A difference is a topology and a forming position of theelastic member.

Specifically, as an impact relieving means, the elastic members 330 and340 are formed on both sides of the reinforcement rib 403, not on theinner surface of the circumferential stopper 310 and the end portion ofthe piston body 200.

A convenience in the installation of the elastic members 330 and 340 isenhanced much more by forming the elastic members 330 and 340 on bothsides of the reinforcement rib 403. Further, the same effect of theimpact relief can be obtained.

FIG. 38 is an enlarged view of the portion “A” FIG. 37. The fundamentaloperation of the friction ring 400 can be performed by spacing apart thereinforcement rib 403 and the elastic members 330 and 340 from theextension bar 300 by a predetermined distance.

FIGS. 39 to 41 illustrate a nineteenth embodiment of the presentinvention.

A structure of the damper for the washing machine according to thenineteenth embodiment of the present invention is mostly similar to thatof the damper according to the first embodiment of the presentinvention. A difference is a connecting method of the piston body 300and the extension bar 200.

FIG. 39 is a sectional view of the damper for the washing machineaccording to the nineteenth embodiment of the present invention.

Referring to FIG. 39, the damper for the washing machine according tothe nineteenth embodiment of the present invention includes a cylinder100, a piston body 200, an extension 300, a friction ring 400, a tubfixing opening 110, a case fixing opening 240, a first friction member210, a second friction member 410, and a circumferential stopper 310,which are similar to the first embodiment of the present invention.However, in this embodiment, the extension bar 300 and the piston body200 is formed as one body. Specifically, the extension bar 300 and thepiston body 200 can be formed as one body by an injection molding. Thecircumferential stopper 310 is a separate element and can be connectedto the circumferential surface of the extension bar 300 by means of aconnection rib 312 formed protrudedly on one side of the circumferentialstopper 310.

Further, the friction ring 400 is pushed by the circumferential stopper310 and the end portion of the piston body 200 in a state that thefriction ring 400 is disposed in the central portion, thereby performingthe multi-step operation of the damper according to the presentsinvention. Except for that, a change of the damping force caused by thedamper is identical to that of the first embodiment.

FIG. 40 is an exploded perspective view of the damper for the washingmachine according to the nineteenth embodiment of the present invention.

Referring to FIG. 40, as described above, the damper according to thepresent invention includes the cylinder 100, the friction ring 400, thepiston body 200, and the extension bar 300. Specifically, the pistonbody 200 and the extension bar 300 are formed as one body at thebeginning of the manufacture.

After the respective elements are disposed at their predeterminedpositions, the connection rib 312 formed protrudedly on one surface ofthe circumferential stopper 310 can be fused on the innercircumferential surface of the end portion of the extension bar 300. Inaddition to the fusion of the circumferential stopper 310, theconnection rib 312 can be connected in other manner, such as bonding.Meanwhile, although the drawing shows the circumferential stopper 310fused on the inner circumferential surface of the extension bar 300, thecircumferential stopper 310 can be practically fused on the outercircumferential surface of the extension bar 300.

This embodiment can obtain a convenience in the manufacture by forming asingle piston, that is, by forming the piston body 200 and the extensionbar 300 as one body.

FIG. 41 is a flowchart illustrating a method for coupling the damper forthe washing machine according to the nineteenth embodiment of thepresent invention.

Referring to FIG. 41, according to the damper of the present invention,the friction ring 400 is inserted into the single piston provided byforming the piston body 200 and the extension bar 300 as one body(ST21). In more detail, the friction ring 400 is formed spaced apartfrom the outer circumference of the extension bar 300 by a predetermineddistance.

The circumferential stopper 310 is arranged in the end portion of theextension bar 300 (ST22). The contact surface between thecircumferential stopper 310 and the extension bar 300 is fused or bondedto connect the circumferential stopper 310 and the extension bar 310(ST23). The process of manufacturing the damper is completed byinserting the single piston into the cylinder 100, in which the frictionring 400 is inserted into the single piston (ST24).

Further, the friction members 210 and 410 formed on the friction ring400 and the outer circumference of the piston body 200 is formedsurrounded around the friction ring 400 and the outer circumference ofthe piston body 200 before the single piston is inserted into thecylinder 100. For this, the friction members 210 and 410 are provided bycoating the porous plastic of the elastic material with a lubricant, asdescribed above. In view of its topology, a rectangular plastic issurrounded at the described-above position.

Meanwhile, the friction ring 400 disposed at the outer circumference ofthe extension bar 300 can be rotated only between the circumferentialstopper 310 and the stepped portion 270. Therefore, when the cylinder100 moves back and forth, the friction ring 400 also moves back andforth together with the cylinder 100. However, the friction ring 400moves in a range between the circumferential stopper 310 and the steppedportion. If the cylinder 100 moves back and forth over a predeterminedlength, the friction ring 400 is pushed by means of the circumferentialstopper 310 and the stepped portion 270, thereby generating a largerdamping force.

As described above, according to the nineteenth embodiment of thepresent invention, the multi-step damper for the washing machine can bemanufactured more easily.

FIG. 42 is a sectional view of a damper for a washing machine accordingto a twentieth embodiment of the present invention.

Referring to FIG. 42, a structure of the damper for the washing machineaccording to the twentieth embodiment of the present invention is mostlysimilar to that of the damper according to the nineteenth embodiment ofthe present invention. A difference is that a connection protrusion 313is formed instead of the connection rib 312. Like this, the moldingprocess of the circumferential stopper 310 can be achieved more easilyby protrudedly forming the connection protrusion 313 on one end of thecircumferential stopper 310 instead of the connection rib 312.

The connection protrusion 313 is not limited to a circular shape shownin the drawing, the connection protrusion 313 can be provided in a shapegiven by recessing an outer circumference of some portion to protrudethe other portion, a triangular shape, a rectangular shape, and thelike.

INDUSTRIAL APPLICABILITY

In the damper for the washing machine according to the presentinvention, an appropriate damping force is applied differently accordingto the case a large amount of vibration occurs and the case a smallamount of vibration occurs during the operation of the damper, therebyrapidly reducing the amount of vibration occurring in the washingmachine.

In addition, since the vibration is rapidly attenuated by applying anappropriate damping force according to an amount of vibration, an amountof noise occurring due to the collision between parts of the washingmachine during the vibration can be reduced, thereby enhancing a goodcondition in the use of the washing machine.

Further, in case a displacement of the damper is large due to a strongvibration, the breakage and damage of the damper can be prevented.

1. A damper for a washing machine, comprising: a cylinder; a piston bodyhaving one end inserted into the cylinder; a first friction memberinterposed in a contact surface between the piston body and thecylinder; an extension bar extended from an inserted portion of thepiston body, the extension bar having a circumferential stopper at theextended portion; a friction ring formed between the circumferentialstopper and the first friction member; and a second friction memberformed on an outer circumferential surface of the friction ring tocontact with an inner surface of the cylinder.
 2. The damper for thewashing machine according to claim 1, further comprising an elasticmember interposed between the friction ring and the circumferentialstopper and/or between the friction ring and the piston body.
 3. Thedamper for the washing machine according to claim 1, wherein theextension bar has a diameter smaller than the piston body.
 4. The damperfor the washing machine according to claim 1, wherein the extension isprovided as a separate part and fixedly inserted into the piston body.5. The damper for the washing machine according to claim 1, furthercomprising a friction ring driving terminal formed by reducing adiameter of the friction ring, at least the circumferential stopperbeing caught by the friction ring driving terminal.
 6. The damper forthe washing machine according to claim 1, further comprising a greaseadhered to an adjacent portion of the friction ring to relieve an impactforce during an operation.
 7. The damper for the washing machineaccording to claim 1, further a friction member interposed in a contactportion between the extension bar and the friction ring.
 8. The damperfor the washing machine according to claim 1, further comprising afriction ring rotation preventing means for preventing a rotation of thefriction ring.
 9. The damper for the washing machine according to claim1, further comprising an elastic member formed on at least an innersurface of the friction ring.
 10. The damper for the washing machineaccording to claim 1, further comprising a reinforcement rib formed onone side of the friction ring to reinforce a strength of the frictionring.
 11. The damper for the washing machine according to claim 1,wherein the extension bar and the piston body are formed as one body.12. The damper for the washing machine according to 1, wherein theextension bar and the piston body are molded as one body.
 13. The damperfor the washing machine according to claim 1, wherein thecircumferential stopper is a separate part and connected to theextension bar.
 14. The damper for the washing machine according to claim1, wherein the friction member is an elastic and porous plastic coatedwith a lubricant.
 15. A damper for a washing machine, comprising: acylinder; a piston body having one end inserted into the cylinder; afirst friction member interposed between the piston body and thecylinder; an extension bar extended from an inserted portion of thepiston body, the extension bar including a circumferential stopperexpandedly formed at a predetermine position of the extended portion; afriction ring formed between the circumferential stopper and the pistonbody and operated by the circumferential stopper and the piston body;and a second friction member interposed in a contact portion between thefriction ring and the cylinder.
 16. The damper for the washing machineaccording to claim 15, further comprising a hook protrusion formedprotrudedly on an outer circumference of the friction ring to support aformation position of the second friction member.
 17. The damper for thewashing machine according to claim 15, further comprising a cooling finformed on an outer circumference of the piston body.
 18. The damper forthe washing machine according to claim 15, wherein first friction memberand/or the second friction member are/is formed by spacing apart two ormore members.
 19. The damper for the washing machine according to claim15, wherein the piston body and the circumferential stopper contact withboth ends of the friction ring.
 20. The damper for the washing machineaccording to claim 15, comprising an elastic member facing a side of thefriction ring and formed on the circumferential stopper and/or an endportion of the piston body.
 21. The damper for the washing machineaccording to claim 15, further comprising a spring formed between thefriction ring and the circumferential stopper and/or between thefriction ring and the piston body.
 22. The damper for the washingmachine according to claim 15, further comprising an elastic membersurrounding an inner circumferential surface and outer surface of thefriction ring, the elastic member being formed as one body.
 23. A damperfor a washing machine, comprising: a cylinder; a piston body having oneend portion inserted into the cylinder and a hollow central portion; afirst friction member interposed between the piston body and thecylinder; an extension bar having one end portion insertedly fixed tothe central portion of the piston body and the other end portionextended from the piston body, the extension bar including acircumferential stopper expandedly formed at the extended end portion; afriction ring formed between the circumferential stopper and the pistonbody and operated by the circumferential stopper and the piston body;and a second friction member interposed in a contact portion between thefriction ring and the cylinder.
 24. The damper for the washing machine,comprising: an elastically deformable opening and or a hook protrusion,the elastically deformable opening being formed at one end portion ofthe extension bar and being elastically deformable; and an insertiongroove formed on the piston body and caught by the hook protrusion. 25.The damper for the washing machine according to claim 23, furthercomprising a cooling hole formed on the piston body to perform a coolingoperation.
 26. The damper for the washing machine according to claim 23,further comprising: an elastic member inserted into the circumferentialstopper; and an elastic member inserted into an end portion of thepiston body.
 27. A method for forming a damper for a washing machine,comprising the steps of: connecting an elastic member to an end portionof a piston body, connecting another elastic member to an extension bar,and placing a friction ring in an outer circumference of the extensionbar; inserting one end portion of the extension bar into the piston bodyto fix the extension bar and the piston body by means of a stopperstructure; and inserting a combination of the extension bar and thepiston body into the cylinder.
 28. The method according to claim 27,further comprising the step of placing a friction member in the frictionring and/or an outer circumference of the piston body in any stepsbefore the combination is inserted into the cylinder.
 29. The methodaccording to claim 28, wherein the friction member is an elastic porousplastic to which a lubricant is adhered.
 30. A damper for a washingmachine, comprising: a cylinder; a piston body having one end portioninserted into the cylinder; a first friction member disposed in acontact surface between the piston body and the cylinder; an extensionbar extended from an inserted portion of the piston body, the extensionbar including a circumferential stopper formed on the extended portion;a friction ring inserted into the cylinder, the friction ring includinga friction ring stopper some portion of which is contracted; and asecond friction member formed on an outer circumferential surface of thefriction ring to contact with an inner surface of the cylinder.
 31. Thedamper for the washing machine according to claim 30, wherein thefriction ring stopper is formed on a portion near to the piston body.32. The damper for the washing machine according to claim 30, whereinthe circumferential stopper is disposed inside the friction ring. 33.The damper for the washing machine according to claim 30, furthercomprising a viscous fluid is adhered to a surrounding of the frictionring stopper.
 34. The damper for the washing machine according to claim30, further comprising an elastic member formed on the circumferentialstopper and/or the piston body.
 35. The damper for the washing machineaccording to claim 30, further a frictional member formed on theextended portion of the extension bar to surfacially contact with aninner circumferential surface of the friction member.
 36. The damper forthe washing machine according to claim 30, further comprising a frictionmember formed at a predetermined position of the extension bar extendedfrom the circumferential stopper.
 37. A damper for a washing machine,comprising: a cylinder; a piston body having one end portion insertedinto the cylinder; a first friction member interposed between the pistonbody and the cylinder; an extension bar extended from an insertedportion of the piston body; a friction ring formed on an outer sidespaced apart from the extension bar; a friction ring rotation preventingmeans for preventing a rotation of the friction ring; and a secondfriction member formed on an outer circumferential surface of thefriction ring to contact with an inner surface of the cylinder.
 38. Thedamper for the washing machine according to claim 37, wherein thefriction ring rotation preventing means includes a non-circular innercircumferential surface of the cylinder and a non-circular outercircumferential surface of the friction ring.
 39. The damper for thewashing machine according to claim 37, wherein the friction ringrotation preventing means includes a non-circular inner circumferentialsurface of the friction ring and a non-circular outer circumferentialsurface of the extension bar.
 40. The damper for the washing machineaccording to claim 37, wherein the friction ring rotation preventingmeans includes an elliptical inner circumferential surface of thecylinder and an outer circumferential surface of the friction ringhaving a shape corresponding to the inner circumferential surface of thecylinder.
 41. The damper for the washing machine according to claim 37,wherein the friction ring rotation preventing means includes an outercircumferential surface of the extension bar and an innercircumferential surface of the friction ring having a shapecorresponding to the outer circumferential surface.
 42. The damper forthe washing machine according to claim 37, wherein the friction ringrotation preventing means includes a spline formed on an innercircumferential surface of the cylinder contacting with the frictionring and/or an outer circumferential surface of the extension bar. 43.The damper for the washing machine according to claim 37, wherein thefriction ring rotation preventing means includes a fixing key formed onan inner circumferential surface of the cylinder contacting with thefriction ring and/or an outer circumferential surface of the extensionbar.
 44. The damper for the washing machine according to claim 37,wherein the friction ring rotation preventing means includes a serrationformed on an inner circumferential surface of the cylinder contactingwith the friction ring and/or an outer circumferential surface of theextension bar.
 45. A damper for a washing machine, comprising: acylinder.; a piston body having one end portion inserted into thecylinder; a first friction member interposed in a contact surfacebetween the piston body and the cylinder; an extension bar extended froman inserted portion of the piston body, the extension bar including acircumferential stopper formed on the extended portion; a friction ringformed between the circumferential stopper and the first frictionmember, the friction ring including a reinforcement rib protrudedlyformed on an inner circumferential surface; and a second friction memberformed on an outer circumferential surface of the friction ring tocontact with an inner surface of the cylinder.
 46. The damper for thewashing machine according to claim 45, wherein the piston body and thecircumferential stopper contact with both end portions of the frictionring during an operation of the damper to thereby make the friction ringoperate.
 47. The damper for the washing machine according to claim 45,further comprising an elastic member formed on an insertion end portionof the piston body and/or an inner surface of the circumferentialstopper.
 48. The damper for the washing machine according to claim 45,wherein the piston body and the circumferential stopper contact withboth end portions of the reinforcement rib to thereby make the frictionring operate.
 49. The damper for the washing machine according to claim45, further comprising an elastic member formed on both sides of thereinforcement rib.
 50. A damper for a washing machine, comprising: acylinder; a piston body having one end portion inserted into thecylinder, and an extension bar extended from the piston body and havinga diameter smaller than the piston body, the piston body and theextension bar being formed as one body; a first friction memberinterposed in a contact surface between the piston body and thecylinder; a friction ring formed between the extension bar and the firstfriction member; and a second friction member formed on an outercircumferential surface of the friction ring and contacting with aninner surface of the cylinder.
 51. The damper for the washing machineaccording to claim 50, wherein the piston body and the extension bar areformed by an injection molding.
 52. The damper for the washing machineaccording to claim 50, further comprising a circumferential stopperconnected to an end portion of the extension bar as a separate part. 53.The damper for the washing machine according to claim 50, furthercomprising a circumferential stopper formed on an end portion of theextension bar, the circumferential stopper being inserted into aninner/outer surfaces of the extension bar.
 54. The damper for thewashing machine according to claim 50, further comprising acircumferential stopper connected to an end portion of the extension baras a separate part to contact with the friction ring.
 55. The damper forthe washing machine according to claim 50, further comprising acircumferential stopper connected to an end portion of the extensionbar, the circumferential stopper having a diameter larger than theextension bar.
 56. The damper for the washing machine according to claim50, further comprising a circumferential stopper fused on an end portionof the extension bar.
 57. A method for forming a damper for the washingmachine, comprising the steps of: inserting a friction ring into anouter side spaced apart from an extension bar; arranging acircumferential stopper in one end of the extension bar to fix thecircumferential stopper; and inserting the extension bar into acylinder.
 58. The method according to claim 57, wherein the extensionbar is injected as one body together with a piston body.
 59. The methodaccording to claim 57, wherein the circumferential stopper is fused onthe extension bar.
 60. The method according to claim 57, wherein theextension bar is formed as one body together with a piston body and astepped portion is formed at a portion in which the extension bar andthe piston body is connected to each other.
 61. The method according toclaim 57, wherein the extension bar has a diameter smarter than thepiston body.